超薄金属-有机骨架纳米片前驱体高效电催化OER反应

金属-有机骨架(MOFs)材料作为前驱体制备特定形貌的纳米材料用于水氧化反应(OER)已成为新的研究热点.使用溶剂热法在泡沫镍基底上合成了超薄的镍钴铁金属-有机骨架(NiCoFe-MOF)纳米片,在保留其纳米片形貌的基础上原位电化学转化为金属氢(羟基)氧化物.在1 mol/L KOH电解液中,10 mA/cm2电流密度时,NiCoFe-MOF纳米片的过电势仅为189 mV,Tafel斜率为35 mV/dec.长时间电解实验表明,NiCoFe-MOF纳米片具有较高的稳定性.原位Raman结果表明,其反应的高活性来源于反应过程中的"活性氧"物种中间体.     

纳米V2O5及其复合电极材料的电化学性能

分别以碳球和葡萄糖为模板剂,采用水热法制备不同形貌的纳米V_2O_5,另外在水热过程直接加入碳纳米管(CNT)和石墨烯(Gr)原位合成CNT/Gr/V_2O_5纳米复合材料。结果表明:碳球和葡萄糖均有还原剂的作用,以碳球为模板制备的试样颗粒呈多层的方玫瑰花状,其在2 mV/s下的比电容达170 F/g;以葡萄糖为模板剂制备的试样呈多孔空心球状,在2 mV/s下的比电容达324 F/g。当葡萄糖浓度为1 mol/L时,原位合成的CNT/Gr/V_2O_5纳米复合材料比表面积高达382.7 m~2·g~(–1),在2 mV/s下的比电容达274 F/g,呈现出良好的电化学性能。     

低温共沉淀法合成多孔CoFe LDH纳米片电催化剂

通过低温共沉淀技术合成了多孔CoFe层状双金属氢氧化物（CoFe LDH）纳米片。运用X射线衍射（XRD）、X射线光电子能谱（XPS）、扫描电镜（SEM）、透射电镜（TEM）等手段对产物的物相、组成及微观形貌进行了表征,并探讨了铁离子（Fe³⁺）含量对CoFe LDH纳米结构生长行为的影响,考察了制备的产物作为电催化剂在电解水析氧反应中的性能。结果表明,Fe³⁺的加入可以有效调节产物的形貌、结晶度和孔道结构。在合适的Co与Fe比例条件下,制备的CoFe LDH可形成多孔纳米片,且增大了总孔体积,增加了表面活性位点。同时,结晶CoFe LDH纳米片可促进Co和Fe离子间的电荷转移行为,从而提高产物的电催化活性。对于电解水析氧反应,当电流密度为10 mA/cm²时,结晶Co_0.67Fe_0.33 LDH多孔纳米片所需的过电势仅为291 mV,Tafel斜率为33 mV/dec,并展现出良好的循环稳定性。     

自牺牲模板法制备氮掺杂碳化钼/碳析氢电催化剂

采用g-C₃N₄为自牺牲模板和氮源，葡萄糖为碳源，钼酸铵为钼源，制备具有二维纳米结构的氮掺杂碳化钼修饰碳纳米片(N-Mo₂C/C)，并评价其电催化析氢性能。利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、透射电镜(TEM)、拉曼(Raman)等测试手段对N-Mo₂C/C的组成、形貌及结构进行分析。结果表明，氮掺杂的Mo₂C纳米颗粒均匀分散在二维碳纳米片上，粒径主要分布在3~5 nm。利用电化学工作站测试 N-Mo₂C/C的电催化析氢性能，在1 mol/L KOH溶液中，电流密度为10 mA/cm²时其对应的过电势为185 mV，Tafel斜率为69 mV/dec，经20 h循环可维持稳定的析氢电势。     

反应晶种法制备Cu-EBTC金属有机框架膜

以多孔Cu O片为支撑体,采用原位生长法和反应晶种法制备Cu-EBTC金属有机框架膜,并利用粉末X射线衍射仪(PXRD)和扫描电子显微镜(SEM))对膜的物相组成和形貌进行表征。实验结果表明:采用原位生长法不能制得连续致密的Cu-EBTC膜,而采用反应晶种法可以成功制得连续致密的Cu-EBTC膜,这是由于在反应中晶种层可以提供大量的晶核。制备得到的Cu-EBTC金属有机框架膜膜厚约为18μm。     

超声化学法快速原位制备形貌可选择的硫化银

利用超声化学技术,在金属Ag片表面快速原位合成不同形貌的Ag2S晶体。借助扫描电子显微镜(SEM)和X-射线衍射仪(XRD)对硫化银晶体的形貌和晶型进行表征和分析。结果表明:生成的Ag2S薄膜致密而牢固;通过改变反应条件(包括:超声照射时间、硫粉的浓度、超声功率、溶剂以及表面活性剂),可以很好地调控产物Ag2S的形貌。该方法简便易行,可望为其他半导体材料的快速原位制备提供一种参考。     

氧化石墨烯生长钨基氧化物酸环境电催化析氢

为了解决商用铂碳电极在电催化析氢反应（HER）领域生产成本高、催化剂使用周期短等问题，利用磷钨酸提供钨源，以单层氧化石墨烯（GO）作为载体，引入利于电子传输轨道的碳纳米管（CNTs），通过一步水热法和空气中煅烧制备得到WO3-rGO-CNTs纳米异质结电催化剂。利用FT-IR、XRD、XPS、TG、SEM、EDAX、TEM和BET对WO3-rGO-CNTs的化学结构和物理形貌进行了表征。结果表明，在单层GO表面均匀生长WO3晶体，并引入CNTs后，纳米异质结WO3-rGO-CNTs在酸性电解质中表现出优异的HER催化活性。利用线性伏安法（LSV）和循环伏安法（CV）对WO3-rGO-CNTs进行HER测试，当电流密度为10 mA/cm2时，其过电势为218 mV；塔菲尔斜率为130.5 mV/dec。当过电势为-0.5 V vs. RHE时，其阻抗值为8.2 Ω。同时，WO3-rGO-CNTs纳米异质结可以在218 mV（电流密度为10 mA/cm2）过电势下，保持50 h的稳定性和耐久性；其双层电容值为1.2 mF/cm2。电化学数据表明，WO3与GO和CNTs间由于异质结构的存在，产生了协同效应：GO为WO3晶体提供了广阔的金属反应活性位点，而CNTs则提供了利于电子传输的活性轨道。     

金属纳米颗粒的形貌控制合成研究进展及催化应用展望

金属纳米材料的性能与其颗粒的形貌密切相关。近年来,研究人员致力于单分散的金属纳米颗粒的形貌控制合成,利用多种方法得到单一不同形貌的金属纳米颗粒。本文综述了金属纳米颗粒的形貌合成进展并展望了其在催化上的应用。     

聚苯胺纳米纤维的合成及表征

以D-樟脑磺酸为掺杂剂,十二烷基苯磺酸钠为软模板,过硫酸铵为氧化剂,在水溶液体系中通过苯胺原位聚合制备得到聚苯胺纳米纤维,对其进行了紫外和红外的表征,并使用SEM对其形貌进行了观测。进一步研究结果表明,樟脑磺酸的掺杂可促进聚苯胺纳米纤维的形成,并同时起到掺杂剂和软模板的双重作用;通过控制反应的时间,可调节产物的形貌结构。     

Pd/WS2二维复合材料的制备及电解水制氢性能研究

首先通过锂离子插层制备了薄层WS_2纳米片,并采用软模板法在纳米片上负载了Pd纳米颗粒,得到Pd/WS_2复合材料。X射线衍射光谱(XRD)和透射电子显微镜(TEM)的结果表明Pd颗粒均匀地负载在了WS_2纳米片上。随后在H_2SO_4水溶液中对该复合材料进行电解水析氢性能测试,线性扫描伏安法(LSV)结果表明:复合材料的析氢起始电位为155 mV,塔菲尔斜率为121.79 mV·dec~(-1),总体催化性能相比于单纯的WS_2纳米片和Pd金属颗粒有很大的改善,也优于当前商用的Pd/C催化剂。采用循环伏安法(CV)测试其稳定性,结果表明Pd/WS_2复合物电极具有优良的电催化析氢稳定性。     

Noble-metal-free cobalt hydroxide nanosheets for efficient electrocatalytic oxidation

Cobalt hydroxide has been emerging as a promising catalyst for the electrocatalytic oxidation reactions, including the oxygen evolution reaction (OER) and glucose oxidation reaction (GOR). Herein, we prepared cobalt hydroxide nanoparticles (CoHP) and cobalt hydroxide nanosheets (CoHS) on nickel foam. In the electrocatalytic OER, CoHS shows an overpotential of 306 mV at a current density of 10 mA·cm^–2. This is enhanced as compared with that of CoHP (367 mV at 10 mA·cm^–2). In addition, CoHS also exhibits an improved performance in the electrocatalytic GOR. The improved electrocatalytic performance of CoHS could be due to the higher ability of the two-dimensional nanosheets on CoHS in electron transfer. These results are useful for fabricating efficient catalysts for electrocatalytic oxidation reactions.     

Ag nanoparticles anchored on MIL-100/nickel foam nanosheets as an electrocatalyst for efficient oxygen evolution reaction performance

Metal-organic frameworks (MOFs) exhibit excellent application potential in the field of electrocatalysis.In this study,we first prepare MIL-100 nanosheets on nickel foam (MIL-100/NF) and then successfully anchor Ag nanoparticles (NPs) on the nanosheets (Ag@MIL-100/NF) for oxygen evolution reaction(OER) catalysis.This strategy dramatically improves the conductivity of MIL-100 and the Ag NPs are uni-formly dispersed on the nanosheets.The Ag@MIL-100/NF catalyst has excellent electrocatalytic perfor-mance and long-term corrosion resistance,with a low overpotential of 207 mV and a long-term stability of at least 100 h at a current density of 50 mA·cm-2.The experimental results demonstrate that this high OER catalytic performance is due to the improved charge transfer after loading Ag NPs,the com-bination of nanosheets and highly dispersed Ag NPs that expose more active sites and the adjusted chem-ical valence states of Fe and Ni in MIL-100.This work provides a surface decoration approach for the preparation of excellent catalysts directly used in the OER.     

MOF nanosheet array-derived NiS with Co,N-doped carbon layer: A highly efficient oxygen evolution electrocatalyst

The development of the hydrogen industry from electrolytic water is confined in great measure to the slow kinetics of oxygen evolution reaction (OER), which means the rational design of a stabilized and efficient OER electrode is the key. The construction of easily accessible hydroxide ion (OH^?) adsorption sites can effectively accelerate the kinetics of the OER. Herein, the NiS/CoNC electrocatalysts, which can effectively adsorb OH^? and exhibited excellent OER performance in an alkaline environment, were obtained by pyrolysis and sulfidation of NiCo-MOF nanosheets on nickel foam (NF). In particular, the optimized NiS/CoNC electrocatalyst achieved an overpotential of 46/106 mV at 10/100 mA cm^?2 and Tafel slope of 57.41 mV dec^?1, which is superior to most reported materials. The outstanding function of OER results from the NiOOH/CoOOH active component generated by surface reconstruction after activation of the NiS/CoNC catalyst and the excellent charge transfer capability of the NiS component. This work offers a scheme to construct the electrocatalysts derived from MOF with excellent OER performance.     

Hierarchical CoP3/NiMoO4 heterostructures on Ni foam as an efficient bifunctional electrocatalyst for overall water splitting

Controllable synthesis strategies of the cost-effective and high-active non-noble metal bifunctional electrocatalysts for overall water splitting are imperatively required. Herein, the hierarchical heterostructure CoP₃/NiMoO₄ nanosheets on Ni foam (CoP₃/NiMoO₄–NF) are synthesized by hydrothermal, annealing and phosphorization treatment. The synergistic effect between CoP₃ and NiMoO₄ remarkably promotes the HER intrinsic activity. Moreover, the Ni foam promotes the vertical growth of well-aligned nanosheet arrays, which expose more active sites for HER and OER. The CoP₃/NiMoO₄–NF-2 (Co/Mo = 1/1) electrocatalyst reveals a low overpotential of 92 mV for HER and 347 mV for OER at 10 mA cm⁻² in 1.0 M KOH. Especially, the CoP₃/NiMoO₄–NF-2 exhibits exceptional performance for overall water splitting which presents a low cell voltage of 1.57 V at 10 mA cm⁻², and outstanding durability which could maintain over 12 h. The design strategy and controllable synthesis of the hierarchical heterostructure bifunctional electrocatalyst will be beneficial for efficient overall water splitting.     

In-situ growth of novel CNTs-graphene hybrid structure on Ni-silica nanocomposites by CVD method for oxygen evolution reaction

Carbon nanostructures are ideal materials for electrochemical reactions like oxygen evolution reaction (OER) due to excellent electrical conductivity, resistance to strong acidic as well as basic conditions and conductive support material for transition metals. In this work we have synthesized multiwalled carbon nanotubes MWCNTs along with graphene growth in-situ by CVD method at 650 °C on nickel-silica nanocomposites for OER in alkaline medium. After removal of silica, our material exhibited comparable OER performance with that of commercial Iridium supported carbon i.e. Ir/C (20 wt % Ir) electrocatalyst. The OER performance is attributed to the defective nature of MWCNTs in the form of surface discontinuities found on rolled graphene layers of carbon nanotubes along with MWCNTs-graphene interfaces which presumably contain dangling bonds as active sites for OER. The overpotential at current density of 10 mA/cm² exhibited by MWCNTs-graphene hybrid carbon nanostructured material was 310 mV in 1 M KOH solution at scan rate of 5 mV/s while commercial Ir/C material revealed overpotential of 305 mV under similar conditions.     

Fabrication of Co doped MoS2 nanosheets with enlarged interlayer spacing as efficient and pH-Universal bifunctional electrocatalyst for overall water splitting

Exploring inexpensive and active bifunctional electrocatalysts to produce hydrogen and oxygen from water at all pHs is highly desirable. Herein, we report a facile one-step method to prepare vertically aligned Co doped MoS₂ nanosheets with extended interlayer distance on carbon cloth (Co–MoS₂@CC) for full hydrolysis in both alkaline and acidic medium. Co–MoS₂@CC exhibits long-term durability with overpotentials of 56.6 mV and 130 mV for hydrogen generation and 242 mV and 201 mV for oxygen production at 10 mA cm^?2 in basic and acidic conditions, respectively. Moreover, we achieve low voltages of 1.585 V and 1.55 V in basic and acidic conditions respectively for the overall water splitting. We assume that such excellent property of Co–MoS₂@CC may be ascribed to the uncovering of more active sites and high porosity resulted from Co doping, which boosts the conductivity and thus reduces MoS₂ hydrogen adsorption free energy in HER, as well as benefits to catalytic active sites in OER. This one-step doping approach opens up new ways to regulate the intrinsic catalytic activity to catalyze total hydrolysis at all PHs.     

Enhanced oxygen evolution reaction performance of synergistic effect of TiO2/Ti3C2/FeNi LDH

The introduction of high-efficiency electrocatalysts can improve the efficiency of oxygen evolution reaction (OER). However, the synergistic effect of elcetrocatalyst and cocatalyst is rarely studied. In this paper, by combining FeNi layered double hydroxide (LDH) electrocatalyst with a two-dimensional (2D) Ti₃C₂ co-catalyst on TiO₂ photocatalyst, the OER performance of TiO₂/Ti₃C₂/FeNi LDH is greatly improved due to the synergistic coupling effect. The microstructure, electrochemical performance and oxygen generation mechanism of TiO₂/Ti₃C₂/FeNi LDH are investigated in this paper. The results showed that the vertical array of FeNi LDH nanosheets created many nanoscale channels for reaction intermediates, enabling them to enter the most active sites on the surface. More importantly, the addition of Ti₃C₂ with high conductivity greatly effectively improved the charge separation and transfer between TiO₂ and FeNi LDH. Therefore, the required over-potential for current density 100 mA/cm² was only 633 mV for TiO₂/2 Ti₃C₂/FeNi LDH. Meanwhile, Tafel slope was as low as 30 mV/dec with good stability. This work provides a reference for using Ti₃C₂ as a new type of co-catalyst material to obtain an efficient, stable and economical OER reaction catalyst.     

电沉积制备多孔Ni-Fe-Sn合金电极及其析氧性能

采用直流电沉积法在铜箔表面合成了多孔结构的Ni–Fe–Sn合金,用扫描电子显微镜、X射线能谱仪和X射线衍射仪对合金的微观组织形貌和相态进行了表征,用电化学工作站测试了合金电极在碱性环境中的析氧性能。结果表明,Ni–Fe–Sn合金电极主要由Ni3Sn2和FeNi3相组成,电极表面形成了多孔结构。在30wt% KOH溶液中,Ni–Fe–Sn合金的析氧过电位仅为261 mV(电流密度10 mA/cm2),Tafel斜率为69.9 mV/dec。电极在10 mA/cm2电流密度下能稳定工作12 h以上,具有良好的电化学稳定性。     

Electrodeposition of catalytically active nickel for the oxygen evolution reaction — effects of anionic composition

Nickel electrodes were prepared by electrodeposition in electrolytes of various anionic compositions. The deposition conditions and bath types were evaluated with special emphasis on the electrocatalytic properties for the oxygen evolution reaction (OER). Electrochemical characterizations in a 5 mol/L KOH solution at 25°C showed that the electrode deposited from the chloride bath, having a low Tafel slope of 50 mV/dec and an overpotential of 396 mV at 100 mA/cm², is the most catalytically active among electrodes prepared in electrolytes of various anionic compositions. The electrode activity for the OER is related to the real surface areas, which depend on the anion compositions in the deposition bath and the deposition conditions.     

Interfacial engineering of transition-metal sulfides heterostructures with built-in electric-field effects for enhanced oxygen evolution reaction

Developing highly efficient,durable,and non-noble electrocatalysts for the sluggish anodic oxygen evo-lution reaction (OER) is the pivotal for meeting the practical demand in water splitting.However,the cur-rent transition-metal electrocatalysts still suffer from low activity and durability on account of poor interfacial reaction kinetics.In this work,a facile solid-state synthesis strategy is developed to construct transition-metal sulfides heterostructures (denoted as MS2/NiS2,M =Mo or W) for boosting OER electro-catalysis.As a result,MoS2/NiS2 and WS2/NiS2 show lower overpotentials of 300 mV and 320 mV to achieve the current density of 10 mA·cm-2,and smaller Tafel slopes of 60 mV·dec-1 and 83 mV-dec-1 in 1 mol·L-1 KOH,respectively,in comparison with the single MoS2,WS2,NiS2,as well as even the bench-mark RuO2.The experiments reveal that the designed heterostructures have strong electronic interac-tions and spontaneously develop a built-in electric field at the heterointerface with uneven charge distribution based on the difference of band structures,which promote interfacial charge transfer,improve absorptivity of OH,and modulate the energy level more comparable to the OER.Thus,the designed transition-metal sulfides heterostructures exhibit a remarkably high electrocatalytic activity for OER.This study provides a simple strategy to manipulate the heterostructure interface via an energy level engineering method for OER and can be extended to fabricate other heterostructures for various energy-related applications.